The present invention relates to a method and apparatus for testing the state of development of a photographic film, the major portion of which is disposed in a light-proof cartridge but which has a leading end that extends out of the cartridge.
When photographic films are processed in large laboratories, the films are removed from the film cartridges in what is called a splicer and cemented together into a long strip. To do this, the trailing end of one film and the leading end of the subsequent film are positioned in a cementing station in such a way that the ends of the respective films can be joined together with a strip of adhesive. Devices of this genus are described in German Published Application No. 3,833,468 and European Published Application No. 0,212,134, for example. The positioning of the films in the splicing station is usually carried out by means of infrared-light barriers.
U.S. Pat. No. 5,093,686 describes a film system and a laboratory organization wherein the film, after being developed and printed, is rewound back into the cartridge and returned to the customer within the original cartridge along with the finished prints. However, this leads to the problem that the laboratory cannot be certain whether a film cartridge that has been delivered to them contains a film that has not yet been developed or an already developed film from which only repeat orders are to be filled.
A splicer that is suitable for such films can be used in darkroom operation, as has been common in the past, to cement the unexposed films into a strip that is then developed in a developing machine. Such a splicer can, however, also be used in a similar way in lightroom operation to splice together into a strip films that repeat orders are to be filled from, whereupon, however, the strip is not to be developed, but printed. If an error occurs during the sorting of incoming film cartridges, such that, for example, a film that has previously been developed is processed with the as-yet undeveloped films or vice-versa, it can lead to the destruction of the incorrectly sorted film. Whereas a film that has already been developed will fade severely when it is developed again, an as-yet unprocessed film that has been mistakenly included with the previously developed films will be exposed as the result of being processed in the lightroom-operation splicer and accordingly completely ruined.
The U.S. Pat. No. 5,521,662 (not a prior publication) discloses a camera. The description mentions an infrared-transmitting sensor that employs various transmission rates to determine whether the film has been developed.